The fully-manual auscultatory method of blood pressure determination was first described by the Russian military surgeon Korotkoff in 1904, but is also called the Rivi-Roci method in honor of the Italian physician who also discovered/invented it at about the same time as Korotkoff. It is called the “fully-manual auscultatory” method because a cuff is manually inflated with a bulb, the cuff is subsequently manually deflated with a valve, and a stethoscope is manually placed distal to the occluding cuff to detect aurally the Korotkoff sounds whose onset signifies the systolic pressure and whose disappearance signify the diastolic blood pressures. In the language of this document this method is referred to as being a member of the fully manual auscultatory (FMA) class and other such abbreviations used in describing my invention are defined below under Classifications of NIBP Devices).
The fully-manual oscillometric (FMO) method was developed, more incrementally than the fully-manual auscultatory method, by many, including notably von Bash, Plesh, Pascal, and Erlanger. Erlanger in 1903 patented a manual oscillometric NIBP device which used a cuff and inflation bulb and deflate valve with an aneroid pressure sensor oscillometer that inscribed the cuff pressure oscillation envelope, superimposed on the cuff pressure, on a smoked drum. This permanent visual record thus permitted the user to visually interpret the oscillogram thus created and hence determine systolic, diastolic, and mean blood pressures noninvasively.
Though Erlanger's oscillometric method and device were elegant, and reported to be very accurate, they were used very little due to the complexity and expense of the apparatus and were effectively doomed to obscurity for almost 75 years. The substantially less cumbersome and less expensive equipment required for the fully-manual auscultatory method, as well as the much easier procedure of the auscultatory method, effectively reduced the practice of the fully-manual oscillometric method (FMO) to a very small following until the late 1970s.
The auscultation of the KS using a stethoscope placed in the antecubital fossa distal to the compressive arm cuff as the pressure is slowly decreased is the essence of the fully-manual auscultatory method (FMA) as published by Korotkoff in 1904, and as still practiced 100 years since its discovery in exactly the same way it was originally described in 1904. When it was discovered, the practice of the new auscultatory method had some major advantages over Erlanger's oscillometric method device. Since the auscultatory method required only a compression cuff and a stethoscope, it could be practiced away from the laboratory, in almost any place really, including the military battle field. All that was required was a semi-cooperative subject and a location quiet enough not to obscure the Korotkoff sounds.
With the advent of the first microprocessors in the early 1970s, and the advent of low cost, laser trimmed, integrated circuit pressure transducers, the technology finally existed to create a fully automatic oscillometric (FAO) device. In 1978 Ramsey published a description of the DINAMAP (Device for Indirect Noninvasive Automatic Mean Arterial Pressure), a fully automatic oscillometric mean arterial pressure (MAP) measuring device, and validated its accuracy in humans with intra-arterial verification. The DINAMAP was the first microprocessor based medical monitor sold commercially and it first entered medical service in March of 1976. The technology developed around FAO devices is the subject of many patents. My inventive new integrated sphygmomanometer, the subject of this document, draws upon some of this prior work, but it is fundamentally different in many respects in its design, in its measurement modes and capabilities. These differences also allow it to be used in circumstances and missions for which the typical FAO device is totally unsuited.
Classification of Non-Invasive Blood Pressure Measuring Devices
In further describing the prior art, it is instructive to review at the various types of noninvasive blood pressure (NIBP) measuring devices which have been produced historically, many of which are still being produced and used today. The utility to the complete disclosure and understanding of my new invention, (and its many operating modes some simultaneously operable) of this historical introduction and the accompanying description of a proposed NIBP device taxonomy will become apparent within the patent application, since both the nomenclature and the NIBP taxonomy and the related abbreviations will be used extensively in describing my invention. Some of these modes of blood pressure measurement are totally new to the art, and others are effectively new by being combined with others to provide a new result. Regardless, the need for a succinct way to refer to these many different modes is needed.
Although this taxonomy and abbreviations of NIBP devices and measurement modes is solely that of the inventor, it is patterned after the taxonomy used in the cardiac pacemaker industry where cardiac pacemakers designs and operational modes are described by three or four letters that represent the functional class of the pacemaker being described. For example, DDD stands for a cardiac pacemaker which is designed for, and capable of implementing if so desired by the physician, cardiac pacing modes described as Dual chamber pacing, Dual chamber sensing, and Dual action i.e., inhibition and triggering based on sensing from dual chambers. A DDDR pacemaker adds a fourth character which in this example stands for Rate responsive.
As is also the case with my new invention, in the case of cardiac pacemakers, not all available modes are necessarily used on each patient, even if the capability is present in the design of the device. The mode(s) used are selected to optimize the cardiac pacing function for patient and circumstance, and for cost of manufacture. For example, a DDDR pacemaker might be implanted in a patient, but, used initially in a VVIO mode where pacing and sensing is being done only in the ventricle and the mode of pacing control is Inhibit only and there is no rate responsiveness of the device. Later in the patient's life with eh pacemaker, the conditions of the patient may change and make other modes more appropriate. By having a multimode device already implanted within the patient, the physician can simply implement the new mode and the patient is spared the expense and risk of implanting a new device that has the required modes for their new clinical circumstance.
Similarly to the cardiac pacemaker field, with the introduction of my new integrated blood pressure measuring device family, and due to the many possible embodiments and their respective modes of operation, there is a great need for a shorthand way of describing the various approaches to design, methods of operation, and modes of measuring blood pressure which are implemented in the design of my new device family, said device family enabling more modes of operation than any prior art device. And, like the cardiac pacemaker, the user of a member of the statMAP family of NIBP devices selects the desired mode(s) of operation when using the device whereby the selected mode is the one(s) most suitable to subject and circumstance at the moment of blood pressure measurement. No prior art device for NIBP provides that versatility.
There are many different types of noninvasive blood pressure measurement (NIBP) devices used in medical practice. NIBP measurement devices include the traditional, fully-manual sphygmomanometers used to implement the manual auscultatory or palpatory or ultrasonic detection methods, and the electronic semi-automatic and fully-automatic devices. These NIBP devices are based on either the auscultatory, ultrasonic method, or the oscillometric method and can be categorized as follows.
Note that all of these existing methods and devices, as well as my inventive device, are based on the detection and interpretation by the user or by a microprocessor of Korotkoff Sounds, ultrasonic flow signals, oscillations in cuff pressure, or palpatory detection during deflation of a blood pressure cuff. Note that not all the methods described below are in use in the prior art devices, and my invention adds several new ones, and usefully combines many of the existing methods to improve measurement reliability or utility depending on the circumstances of measurement, including the physiologic state of the subject as well as the environment in which they are being measured.
A taxonomy of NIBP devices follows. It is the case that each of the modes and methods are available in at least one embodiment of the statMAP family, and in most embodiments, two or more of these BP measurement methods and modes are available by user selection and use depending on the needs of the clinical circumstances.